This study has three specific aims: 1. to complete the characterization of the natural history of medication compliance in a large prospective cohort of kidney transplant recipients, 2. to characterize the relationship between noncompliant behavior and adverse clinical events in these patients, and 3. to test the clinical efficacy of a behavioral intervention in patience with demonstrated noncompliance. Using microelectronic medication monitors, we will continue to gather prospective data on medication compliance in an active, prospective cohort of 140 renal transplant patients. We will complete 4 years of data collection for each patient. We will continue to analyze those data and examine the correlations between compliance behavior and graft rejection, graft loss and patient death. To date we have shown that noncompliant behavior is significantly associated, in a dose response manner, with decreased rejection-free survival rates, and increased graft loss. Further, compliance behavior as early as the third month posttransplant predicts the later events. Additionally, later acute rejection episodes, known to be associated with chronic rejection and graft loss, are clustered with the least compliant patients. These studies (Aims#1 and #2) support proposing an intervention trial modeled after the successful approach of the Diabetes Control and Complications Trial (DCCT) focusing behavior modification strategies on those patients with the early predictors of noncompliance. The goal is to intervene at a personal level and change the patients' behavior with the expectation that improved compliance behavior will reduce the occurrence of later rejections and associated graft loss. An effective intervention after transplantation is especially appealing since it focuses resources on uniquely high risk noncompliant patients.